Traditional asset tracking systems commercially available and commonly used typically utilize either radio frequency identification (hereinafter, “RFID”) tags or global positioning system (hereinafter, “GPS”) components for tracking items.
Generally, systems utilizing RFID tags require movement of tagged assets to within a few feet of a fixed reader or movement of the reader to within a few feet of the tagged assets. Further, confusion often results when several tagged assets are in close proximity. Moreover, it will be appreciated that systems utilizing RFID tags are limited by poor scalability, poor wireless security, RF noise and interference, lack of real-time alerting, poor ability to adjust to changes in number and configuration of tagged assets, poor sensor integration capability, and high infrastructure requirements.
Systems utilizing GPS generally are no more ideal, as GPS requires line-of-sight reception from multiple satellites, which limits system utility with assets that are located indoors or in other obscured sites. Indeed, it will be appreciated that systems utilizing GPS are limited by its high consumption of battery power, high device costs, high operating costs, and need for a separate data communications link to report asset position and/or to report sensor data.
It will still further be appreciated that despite recent advances in ad hoc networking in point-to-point communications as applied to asset tracking, the tracking of large numbers (i.e., thousands) of movable/moving assets via the monitoring of sensors attached thereto still posed significant challenges prior to the CBN and WU technologies of the incorporated patents and published patent applications.
In this respect, ad hoc wireless networks generally support point-to-point (i.e., node-to-node) communications without central control. Because nodes in wireless ad hoc networks are generally unconstrained by wires, communications is possible with nodes attached to mobile assets. Moreover, such communications are possible even as the assets and/or nodes move or are moved to new locations and even when the nodes change configurations. Consequently, wireless ad hoc networks allow for both quick network deployment and adjustment to the dynamic comings, goings, and re-positioning of the assets and/or the nodes.
Wireless ad hoc networks tend to be relatively inexpensive, fault-tolerant, and flexible. However, commonly used random-access protocols and the design and/or selection of radios to support such networks are often not well coordinated, with the result frequently being a sub-optimized network topology and constrained applications. Additionally, such networks typically organize on the basis of either physical proximity of the nodes or received signal strength. All of these factors introduce added latency, reduced throughput, and increased (and avoidable) transmissions and interference. As more nodes enter the network, these impairments are aggravated, and with each added transmission, battery power of the mobile nodes is consumed.
The use of spread spectrum techniques, either Frequency Hopping Spread Spectrum (hereinafter, “FHSS”) or Direct Sequence Spread Spectrum (hereinafter, “DSSS”), mitigates some of these impairments.
A node employing FHSS repeatedly changes frequencies during transmissions (i.e., from one sub-channel to another) per an interference-avoiding algorithm that is utilized by all nodes of the same network. However, although FHSS can be very effective in minimizing interference (or deliberate jamming), all nodes must have the same algorithm, which has the effect of excluding whole categories of potential network users in commercial applications.
A node employing DSSS operates similarly but transmits on multiple frequencies according to the nature of the data to be sent, rather than explicitly avoiding interference. DSSS has the effect of minimizing interference, but has the disadvantage of needing the transmitting power of all nodes to be approximately equal, or else signal-blocking can result.
The CBN and WU technologies of the incorporated patents and published patent applications tend to address these noted drawbacks to ad hoc wireless networks, and are described in further detail below, as one or more preferred embodiments of the present invention utilize such technologies.